A ball is kicked straight up.  The ball's speed decreases as it moves upward.  Why does the ball's speed decrease?

A.  Because one or more forces are acting to slow the ball down

B.  Because a force given to the ball by the kick completely runs out

C.  Because a force given to the ball by the kick becomes equal to the force of gravity

D.  Because a force given to the ball by the kick becomes less than the force of gravity